LONDON, June 15 The amount of euro-denominated investment-grade corporate bonds with negative yields has tripled over the last six weeks, a move accelerated by their inclusion in the European Central Bank's quantitative easing programme.

Around 16 percent, or 440 billion euros ($494 billion), of the 2.8 trillion euros of these bonds now yield less than zero, up from around 5 percent at the start of May, according to Tradeweb data.